Method for producing blends of phthalic acid diesters, decanols and tridecanols

ABSTRACT

A process is described for preparing mixtures of diesters of phthalic acid with decanols and tridecanols by reacting phthalic acid or a reactive derivative of phthalic acid with a mixture made from at least one decanol and at least one tridecanol.  
     Mixtures obtainable in this way are also described, as is their use as plasticizers for molding compositions, and also mixtures of isomeric tridecanols suitable for preparing the mixtures of diesters.

[0001] The present invention relates to a process for preparing mixturesof diesters of phthalic acid with decanols and tridecanols.

[0002] The present invention further relates to mixtures of this typeand to their use as plasticizers for molding compositions, and also tomixtures of isomeric tridecanols suitable for preparing the mixtures ofdiesters.

[0003] Long-chain alcohols, e.g. C₁₀, C₁₁, or C₁₃ alcohols, are widelyused for preparing plasticizers. To this end, the alcohols are reactedwith polycarboxylic acids, such as in particular phthalic acid, to givethe corresponding esters.

[0004] Important members of this phthalate class of plasticizers arediisodecyl phthalates and diisotridecyl phthalates. They are mainly usedin producing cable sheathing, and lines or pipes made from polyvinylchloride (PVC), for example in automotive construction.

[0005] The prior art includes phthalate plasticizers whose alcohol unitsare C₁₀ alcohols (decanols) or C₁₃ alcohols (tridecanols):

[0006] JP-A 07 179 699 and JP-A 08 283 510 describe PVC-filmplasticizers which are diesters of phthalic acid with a mixture composedof the C₁₀ alcohols 2-propylheptanol and 4-methyl-2-propylhexanol in aratio by weight of from 88:12 to 70:30. JP-A 08 301 295 describes theuse of esters of this type as plasticizers for PVC, in which the ratioby weight of 2-propylheptanol and 4-methyl-2-propylhexanol is from 100:0to 50:50. JP-A 08 034 891 also discloses a PVC-film plasticizer based on2-propylheptanol and 4-methyl-2-propylhexanol, and, in addition, aplasticizer of this type which contains 2-propylheptanol as sole alcoholunit.

[0007] JB 73/35705 and JA 81/47443 disclose the use of the diester ofphthalic acid with tridecanol as a plasticizer for vinyl chloridepolymers, such as PVC.

[0008] The skilled worker in the sector of PVC plastics, especially oneconcerned with the production of films, cables or lines made from thismaterial, is increasingly frequently faced with the task of usingplasticizers which on the one hand improve the plastic properties ofthese materials, primarily their low-temperature flexibility, but whichon the other hand have only low volatility. Relatively low volatility issignificant in helping to ensure that the flexibility achieved when thePVC plastic is prepared is retained in the long term, and that there ispractically no emission of the plasticizer into the environment.

[0009] Known phthalate plasticizers with decanols or tridecanols asalcohol unit remain unsatisfactory in this regard.

[0010] It is an object of the present invention, therefore, to provideplasticizers which are based on esters of phthalic anhydride withalcohols having 10 or more carbon atoms and which can overcome thedisadvantage described.

[0011] We have found that this object is achieved by means of a processfor preparing mixtures of diesters of phthalic acid with decanols andtridecanols, which comprises reacting phthalic acid or a reactivederivative of phthalic acid with a mixture composed of at least onedecanol and at least one tridecanol.

[0012] Mixtures of this type have also been found, as has their use as aplasticizer for molding compositions, and also mixtures of isomerictridecanols suitable for preparing the mixtures of diesters.

[0013] The plasticizers of the invention bring about highlow-temperature flexibility and have low volatility, superior to thoseof phthalic esters made from decanols alone or from tridecanols alone.

[0014] Preferred decanols are aliphatic monoalcohols having 10 carbonatoms, in particular the primary alkanols, the alkyl groups of which maybe straight-chain or branched, for example n-decanol, methylnonanols,such as 1-methylnonanol, ethyl octanols, such as 1-ethyloctanol,propylheptanols, such as 1-propylheptanol, or methylpropylhexanols, ineach case individually or in a mixture, and especially 2-propylheptanolon its own or 4-methyl-2-propylhexanol on its own. Particular preferenceis given to mixtures of the alcohols mentioned (“isodecanols”),particularly those with the CAS numbers 25339-17-7 and 93821-11-5. Veryparticular preference is given to mixtures in which 2-propylheptanol and4-methyl-2-propylhexanol are present jointly and predominantly,preferably making up 80% by weight, especially 90% by weight, and inparticular 95% by weight, and specifically in a ratio of from 99:1 to1:99% by weight, preferably from 95:5 to 50:50% by weight, andparticularly preferably from 92:8 to 88:12% by weight.

[0015] Preferred tridecanols are aliphatic monoalcohols having 13 carbonatoms, in particular the primary alkanols, the alkyl groups of which maybe straight-chain or branched, for example n-tridecanol, methyldecanols[sic], such as 1-methyldodecanol, or ethylundecanols, such as1-ethylundecanol, in each case either individually or in a mixture.Preference is given to mixtures of the alkanols mentioned(“isotridecanols”), and in particular those with the CAS numbers27458-92-0 and 68526-86-3. Particular preference is given toisotridecanols obtainable by the following process:

[0016] In a multistage process starting from a hydrocarbon mixturecomprising butenes, a first step dimerizes the butenes to give a mixtureof isomeric octenes and dodecenes. The main product produced here is theoctenes, while the proportion of dodecenes produced is generally from 5to 20% by weight, based on the reactor discharge. The dodecenes are thenisolated from the reaction mixture, hydroformylated to give thecorresponding C₁₃ aldehydes, and then hydrogenated to giveisotridecanols. The preparation of isotridecanols by this sequence ofsynthetis steps is known per se. However, the isotridecanolsparticularly preferred according to the invention are to be obtainedonly if specific defined parameters are complied with at least duringthe butene dimerization, and preferably during the butene dimerizationand the hydroformylation.

[0017] It is therefore preferable to obtain the mixture of isomericdodecenes by bringing a hydrocarbon mixture comprising butenes intocontact with a heterogeneous catalyst which comprises nickel oxide. Theisobutene content of the hydrocarbon mixture is preferably 5% by weightor less, in particular 3% by weight or less, particularly preferably 2%by weight or below, and most preferably 1.5% by weight or less, based ineach case on the total butene content. A suitable hydrocarbon stream iswhat is known as the C₄ cut, a mixture composed of butenes and butanes,which is available in large amounts from FCC plants or steam crackers.Particular preference is given to the use of raffinate II as startingmaterial, this being an isobutene-impoverished C₄ cut.

[0018] One preferred starting material comprises from 50 to 100% byweight, preferably from 80 to 95% by weight, of butenes, and from 0 to50% by weight, preferably from 5 to 20% by weight, of butanes. Thefollowing composition of the butene fraction may be given as a generalquantitative guideline: 1-butene from 1 to 99% by weight cis-2-butenefrom 1 to 50% by weight trans-2-butene from 1 to 99% by weight isobutenefrom 1 to 5% by weight.

[0019] Catalysts which may be used are catalysts known per se whichcomprise nickel oxide, e.g. as described by O'Connor et al. in CatalysisToday 6, (1990) p. 329. Supported nickel oxide catalysts may be used,suitable support materials being silica, alumina, aluminosilicates,aluminosilicates with a phyllosilicate structure, and zeolites.Particularly suitable catalysts are precipitation catalysts obtained bymixing aqueous solutions of nickel salts and silicates, e.g. mixingsodium silicate and nickel nitrate, where appropriate with otherconstituents, such as aluminum salts, e.g. aluminum nitrate, andcalcining.

[0020] Particular preference is given to catalysts substantiallycomposed of NiO, SiO₂, TiO₂ and/or ZrO₂, and also, where appropriate,Al₂O₃. Most preference is given to a catalyst whose active substantialconstituents are from 10 to 70% by weight of nickel oxide, from 5 to 30%by weight of titanium dioxide and/or zirconium dioxide, and from 0 to20% by weight of aluminum oxide, the remainder, to give 100% by weight,being silicon dioxide. A catalyst of this type is obtainable byprecipitating the catalyst composition at a pH of from 5 to 9 by addingan aqueous solution comprising nickel nitrate to an alkali metal waterglass solution which comprises titanium dioxide and/or zirconiumdioxide, filtering, drying and annealing at from 350 to 650° C.Reference is made to DE-A 43 39 713 for details of the preparation ofthese catalysts. Reference is made to the entire disclosure of thatpublication.

[0021] The hydrocarbon mixture comprising butenes is preferably broughtinto contact with the catalyst at from 30 to 280° C., in particular from30 to 140° C., and particularly preferably from 40 to 130° C. Thepressure here is preferably from 10 to 300 bar, in particular from 15 to100 bar, and particularly preferably from 20 to 80 bar. This pressure isusefully adjusted so that the olefin-rich hydrocarbon mixture is liquidor in the supercritical state at the temperature selected.

[0022] Examples of suitable apparatuses for bringing the hydrocarbonmixture comprising butenes into contact with the heterogeneous catalystare tube-bundle reactors and shaft furnaces. Shaft furnaces arepreferred because the capital expenditure costs are lower. Thedimerization may be carried out in a single reactor, where theoligomerization catalyst may have been arranged in one or more fixedbeds. Another way is to use a reactor cascade composed of two or more,preferably two, reactors arranged in series, where the butenedimerization in the reaction mixture is driven to only partialconversion on passing through the reactor or reactors preceding the lastreactor of the cascade, and the desired final conversion is not achieveduntil the reaction mixture passes through the last reactor of thecascade. The butene dimerization preferably takes place in an adiabaticreactor or in an adiabatic reactor cascade.

[0023] After leaving the reactor or, respectively, the last reactor of acascade, the dodecenes formed are separated off from the octenes and,where appropriate, from the higher oligomers, and from the unconvertedbutenes and butanes, in the reactor discharge. The octenes are generallythe main product.

[0024] In the second step of the process, the dodecenes obtained areconverted in a manner known per se into the aldehydes with moleculeslengthened by one carbon atom, by hydroformylation using synthesis gas.The hydroformylation of olefins to prepare aldehydes is known per se andis described in J. Falbe (Ed.): “New Synthesis with Carbon monoxide”,Springer Verlag, Berlin, 1980, for example. The hydroformylation takesplace in the presence of catalysts dissolved homogeneously in thereaction medium. The catalysts used here are generally compounds orcomplexes of metals of the transition group VIII, especially compoundsor, respectively, complexes of Co, Rh, Ir, Pd, Pt or Ru, these beingeither unmodified or modified with, for example, amine- orphosphine-containing compounds.

[0025] For the purposes of the present invention, the hydroformylationpreferably takes place in the presence of a cobalt catalyst, preferablyat from 120 to 240° C., in particular from 160 to 200° C., under asynthesis-gas pressure of from 150 to 400 bar, in particular from 250 to350 bar. The hydroformylation preferably takes place in the presence ofwater. The mixing ratio of hydrogen to carbon monoxide in the synthesisgas used is preferably in the range from 70:30 to 50:50% by volume andin particular from 65:35 to 55:45% by volume.

[0026] The cobalt-catalyzed hydroformylation process may be carried outas a multistage process which comprises the following 4 stages:preparation of the catalyst (precarbonylation), catalyst extraction,olefin hydroformylation, and catalyst removal from the reaction product(decobaltization). In the first stage of the process, theprecarbonylization, the starting material used is an aqueous cobalt saltsolution, e.g. cobalt formate or cobalt acetate, which is reacted withcarbon monoxide and hydrogen to prepare the catalyst complex (HCo(CO)₄)needed for the hydroformylation. In the second stage of the process, thecatalyst extraction, the cobalt catalyst prepared in the first stage ofthe process is extracted from the aqueous phase using an organic phase,preferably using the olefin to be hydroformylated. Besides the olefin,it is sometimes useful to use the reaction products and byproducts fromthe hydroformylation for catalyst extraction, as long as these areinsoluble in water and liquid under the selected reaction conditions.After separation of the phases, the organic phase loaded with the cobaltcatalyst is fed to the third stage of the process, the hydroformylation.In the fourth stage of the process, the decobaltization, the organicphase of the reactor discharge is freed from the cobalt carbonylcomplexes in the presence of complex-free process water by treatmentwith oxygen or air. During this, the cobalt catalyst is oxidativelybroken down and the resultant cobalt salts are extracted back into theaqueous phase. The aqueous cobalt salt solution obtained from thedecobaltization is recirculated into the first stage of the process, theprecarbonylation. The crude hydroformylation product obtained may be feddirectly to the hydrogenation. As an alternative, a C₁₃ aldehydefraction may be isolated from this in a usual manner, e.g. bydistillation, and fed to the hydrogenation.

[0027] The formation of the cobalt catalyst, the extraction of thecobalt catalyst into the organic phase, and the hydroformylation of theolefins may also be carried out in a single-stage process in thehydroformylation reactor.

[0028] Examples of cobalt compounds which may be used are cobalt(II)chloride, cobalt(II) nitrate, the amine or hydrate complexes of these,cobalt carboxylates, such as cobalt formate, cobalt acetate, cobaltethylhexanoate, or cobalt naphthenoate, and also the cobaltcaprolactamate complex. Under the hydroformylation conditions, thecatalytically active cobalt compounds form in situ as cobalt carbonyls.It is also possible to use the carbonyl complexes of cobalt, such asdicobalt octacarbonyl, tetracobalt dodecacarbonyl, or hexacobalthexadecacarbonyl.

[0029] The aldehyde mixture obtained during the hydroformylation isreduced to give primary alcohols. Some degree of reduction generallytakes place under the hydroformylation conditions, and thehydroformylation here may also be controlled so that substantiallycomplete reduction takes place. However, the hydroformylation productobtained is generally hydrogenated in another step of the process usinghydrogen gas or a gas mixture comprising hydrogen. The hydrogenationgenerally takes place in the presence of a heterogeneous hydrogenationcatalyst. The hydrogenation catalyst used may be any desired catalystsuitable for hydrogenating aldehydes to give primary alcohols. Examplesof suitable catalysts available commercially are copper chromite,cobalt, cobalt compounds, nickel, nickel compounds, which may, whereappropriate, comprise small amounts of chromium or other promoters, andmixtures of copper, nickel, and/or chromium. The nickel compounds aregenerally in supported form on support materials such as alumina orkieselguhr. It is also possible to use catalysts comprising preciousmetals, such as platinum or palladium.

[0030] The hydrogenation may take place by the trickle-flow method,where the mixture to be hydrogenated and the hydrogen gas or,respectively, the hydrogen-containing gas mixture are passed, forexample concurrently, over a fixed bed of the hydrogenation catalyst.

[0031] The hydrogenation preferably takes place at from 50 to 250° C.,in particular from 100 to 150° C., and at a hydrogen pressure of from 50to 350 bar, in particular from 150 to 300 bar. Fractional distillationcan be used to separate the desired isotridecanol fraction from the C₈hydrocarbons and higher-boiling products present in the reactiondischarge obtained during the hydrogenation.

[0032] The resultant isotridecanols particularly preferred for thepurposes of the present invention have a characteristic distribution ofisomers, which can be defined in more detail by means of gaschromatography, for example. The gas chromatogram can be divided intothree retention regions, for example as described by Kovacs (Z. Anal.Chem. 181, (1961), p. 351; Adv. Chromatogr. 1 (1965), p. 229) with theaid of retention indices and using n-undecanol, n-dodecanol, andn-tridecanol as reference substances: Region 1: Retention index <1180Region 2: Retention index from 1180 to 1217 Region 3: Retention index>1217

[0033] The substances present in region 1 are mainly triply andmore-than-triply branched isotridecanols, those present in region 2 aremainly doubly branched isotridecanols, and those present in region 3 aremainly singly-branched isotridecanols and n-tridecanol. For the purposesof the present invention, this method gives an adequately precisedetermination of the composition of isotridecanols by comparing theareas under the corresponding sections of the gas chromatogram curves (%by area).

[0034] Using the Kovacs method described, the particularly preferredisotridecanols of the invention generally have from 20 to 60% by area,preferably from 25 to 50% by area, particularly preferably from 40 to48% by area, and very particularly preferably from 45 to 47% by area, oftriply and more-than-triply branched isomers.

[0035] Using the Kovacs method described, the particularly preferredisotridecanols of the invention generally have from 10 to 50% by area,preferably from 20 to 45% by area, particularly preferably from 30 to40% by area, and very particularly preferably from 35 to 38% by area, ofdoubly branched isomers.

[0036] Using the Kovacs method described, the particularly preferredisotridecanols of the invention generally have from 5 to 30% by area,preferably from 10 to 25% by area, particularly preferably from 15 to20% by area, and very particularly preferably from 17 to 19% by area, ofsingly branched isomers and n-tridecanol.

[0037] The density of the particularly preferred isotridecanols isgenerally from 0.8 to 0.9 g/cm³, preferably from 0.82 to 0.86 g/cm³, andparticularly preferably from 0.84 to 0.845 g/cm³. Their refractive indexn_(D) ²⁰ is generally from 1.4 to 1.5, preferably from 1.44 to 1.46, andparticularly preferably from 1.446 to 1.45. Their viscosity is generallyfrom 30 to 40 mpas, preferably from 32 to 38 mpas, and particularlypreferably from 34 to 35.5 mpas. Their boiling range is generally from240 to 280° C., preferably from 250 to 275° C., and particularlypreferably from 260 to 270° C.

[0038] The inventive diesters of phthalic acid are prepared in a mannerknown per se, by esterifying phthalic acid or a reactive phthalic acidderivative, such as phthalic anhydride or phthalic dichloride, using amixture composed of at least one decanol and at least one tridecanol. Itis preferable for the phthalic acid or the reactive phthalic acidderivative to be reacted with a molar excess of the alcohols, inparticular a molar excess of from 5 to 30%, preferably in the presenceof a Lewis acid as esterification catalyst, for example a dialkyltitanate, e.g. isopropyl butyl titanate, or of a Brönsted acid, such asmethanesulfonic acid or sulfuric acid.

[0039] The reaction of the phthalic acid or of the reactive derivativeof phthalic acid with the mixture made from at least one decanol andfrom at least one tridecanol generally takes place at from 150 to 300°C., preferably from 200 to 250° C.

[0040] It is preferable to use a molar excess of from 20 to 30%,preferably about 25%, of the mixture made from at least one decanol andfrom at least one tridecanol, based on phthalic acid or on the reactivederivative of phthalic acid.

[0041] An inert gas, such as nitrogen, may be passed through thereaction mixture during the reaction for continuous removal of waterproduced during the esterification process.

[0042] Once the reaction has ended, the reaction mixture is worked up togive the inventive mixture of esters of phthalic acid. The procedurehere generally begins with very substantial removal particularly oforganic contaminants and, where appropriate, unreacted decanol and/ortridecanol. This is preferably achieved by distilling off the excessalcohol in vacuo. The distillation is generally carried out at from 150to 220° C., preferably from 180 to 200° C., at a pressure which isgenerally from 10 to 100 mbar, preferably from 40 to 60 mbar.

[0043] The crude ester mixture is then generally treated and thoroughlymixed with an aqueous alkali metal hydroxide solution, e.g. 1 percentstrength by weight sodium hydroxide solution, the result being that thehalf ester and the catalyst are neutralized (and, where appropriate,hydrolyzed). It is normal for an aqueous phase and an organic phase tobe formed here, the aqueuos phase being removed. A water wash of theorganic phase may follow.

[0044] For further purification, the acid-free and washed ester mixtureis preferably freed from organic contaminants and residual alcohols bystripping, using inert gas or steam. In a typical embodiment of thisstripping procedure, the crude product is fed to the head, or to thevicinity of the head, of the stripping column, and nitrogen or steam isconducted in countercurrent through the column. The stripping procedureis generally carried out with a starting temperature for the crudeproduct of from 130 to 220° C., preferably from 170 to 190° C., and at apressure of from 10 to 100 mbar, preferably from 20 to 40 mbar. If thestripping time exceeds 2 hours in batchwise conduct of the process inthe presence of water within the reaction mixture, the acid value of theproduct generally rises undesirably. The acid produced then has to bereneutralized, and the water removed from the neutralization process.

[0045] The purified ester mixture may then be dried at an elevatedtemperature in vacuo by passing a stream of nitrogen through thematerial, and, where appropriate, further purified by contact with anadsorbent, such as activated carbon or bleaching earth.

[0046] The molar ratio of decanols and tridecanols in the alcoholmixture used according to the invention is generally from 95:5 to 5:95,preferably from 85:15 to 15:85, particularly preferably from 75:25 to25:75, and very particularly preferably from 75:25 to 65:35.

[0047] On the basis of a general knowledge of chemistry it may beassumed that the alcohols used according to the invention for preparingthe ester mixtures do not all have the same reactivity towards thephthalic acid or the reactive derivative of phthalic acid, particularlysince the alcohols have different electronic and stearic features.However, for practical purposes the composition of the ester mixturegenerally reflects sufficiently the composition of the alcohol mixtureused for preparing the ester mixture.

[0048] The ester mixtures of the invention prepared in this waypreferably comprise diesters of phthalic acid having in each case onedecanol unit and one tridecanol unit, and also diesters having twodecanol units or having two tridecanol units. If use is made of analcohol mixture which is composed of from 60 to 70% by weight ofdecanols and from 30 to 40% by weight of tridecanols, the productsobtained generally have the following composition:

[0049] from 38 to 45% by weight of diesters with two C₁₀ alcohols, from40 to 48% by weight of diesters with one C₁₀ and one C₁₃ alcohol, andfrom 12 to 15% by weight of diesters with two C₁₃ alcohols.

[0050] The process of the invention and the purification operationsdescribed can generally prepare ester mixtures with ester contents ofmore than 99.5% by weight.

[0051] If use is made of mixtures made from isomeric decanols and fromisomeric tridecanols, a wide variety of ester mixtures is accessible.All of these ester mixtures are encompassed by the present invention.They are composed of phthalic esters which therefore can differ bothwith regard to the number of carbon atoms in the alcohol units of theester groups and with regard to the branching of the alkyl chains withinthese alcohol units.

[0052] By using mixtures composed of isomeric decanols and isomerictridecanols it is possible to obtain a wide variety of ester mixtures.All of these ester mixtures are included in the present invention. Thesemixtures are made of phthalic esters which may differ either with regardto the number of carbon atoms in the alcohol units within the estergroups or else with regard to the branching of the alkyl chains withinthese alcohol units.

[0053] The diester mixtures of the invention generally have a density offrom 0.94 to 0.97 g/cm³ preferably from 0.945 to 0.965 g/cm³, and inparticular from 0.95 to 0.96 g/cm³, a viscosity of from 100 to 200 mPas,preferably from 120 to 180 mPas, and in particular from 130 to 160 mPas,and a refractive index n_(D) ²⁰ of from 1.475 to 1.495, preferably from1.48 to 1.49, and in particular from 1.482 to 1.484.

[0054] The diester mixtures of the invention are suitable asplasticizers for molding compositions, in particular for PVC-basedmolding compositions. They are particularly suitable for preparingplasticized PVC compounds intended to have low plasticizer volatilitytogether with very good cold-flexibility properties. The followingmethod is preferably employed for preparing and testing the plasticizedPVC compounds prepared using the diesters of the invention:

[0055] A mixture is prepared composed of PVC powder, preferably of a PVCpowder prepared by the suspension process, and of an inventive diesterof phthalic acid as plasticizer. Other additives may be added ifdesired, for example stabilizers, lubricants, fillers, pigments, dyes,flame retardants, light stabilizers, antistats, blowing agents, andbiostabilizers. This mixture is then plasticized on a roll mill androll-milled to give what is known as a milled sheet. The milled sheet isthen pressed to give a plasticized PVC film, on which the performancetests are then carried out.

[0056] The cold-flexibility properties of plasticized PVC compounds arepreferably characterized using what are known as the cold-cracktemperature and the torsional rigidity.

[0057] The cold-crack temperature is the temperature at which aplasticized PVC compound begins to show visible damage under mechanicalload at low temperatures. The cold-crack temperature was determined hereto DIN 53372.

[0058] The torsional rigidity is the temperature at which a plasticizedPVC compound can be twisted through a certain angle when a particulardefined force is applied, and was determined here to DIN 53447.

[0059] Examples will now be used below to illustrate the invention infurther detail:

EXAMPLES Example 1 Preparation of a Mixture of Isomeric Tridecanols

[0060] Process Step 1 (Butene Dimerization)

[0061] The butene dimerization was carried out continuously in anadiabatic reactor composed of two subsidiary reactors (length: each 4 m,diameter: each 80 cm) with intermediate cooling at 30 bar. The startingmaterial used was a raffinate II with the following composition:i-butane  2% by weight n-butane 10% by weight i-butene  2% by weight1-butene 32% by weight trans-2-butene 37% by weight cis-2-butene 17% byweight

[0062] The catalyst used comprised a material as in DE-A 43 39 713,composed of 50% by weight of NiO, 12.5 % by weight of TiO₂, 33.5% byweight of SiO₂ and 4% by weight of Al₂O₃, in the form of 5×5 mm tablets.The reaction was carried out with a throughput of 0.375 kg of raffinateII per liter of catalyst and hour, and with recycling of the reactordischarge freed from the oligomers formed, with a recycling ratiorecycled material and raffinate II of 3, and with an entry temperatureof 38° C. at the first subsidiary reactor, and with an entry temperatureof 60° C. at the second subsidiary reactor. Conversion, based on thebutenes present in the raffinate II, was 83.1%, octene selectivity was83.3%, and dodecene selectivity was 12%. Fractional distillation of thereactor discharge was used to separate the dodecene fraction fromunconverted raffinate II, the octenes and the high-boilers.

[0063] Process Step 2(Hydroformylation Followed by Hydrogenation)

[0064] 750 g of the dodecene mixture prepared in step 1 of the processwere reacted for 5 hours batchwise in an autoclave with 0.13% by weightof dicobalt octacarbonyl (Co₂(CO)₈) as catalyst, with addition of 75 gof water, at 185° C. and under a synthesis-gas pressure of 280 bar, witha mixing ratio H₂ and CO of 60:40% by volume. The consumption ofsynthesis gas, detectable by a pressure fall-off in the autoclave, wascompensated by introducing more gas under pressure. Once the pressure inthe autoclave had been reduced, the reactor discharge, with 10% strengthby weight of acetic acid, was freed oxidatively from the cobalt catalystby introducing air, and the organic product phase was hydrogenated usingRaney nickel at 125° C. and with a hydrogen pressure of 280 bar for 10h. Fractional distillation of the reactor discharge was used to separatethe isotridecanol fraction from the C₁₂ paraffins and the high boilers.

[0065] Using the Kovacs method (see above) to determine percentage areasfrom gas chromatography, the proportion of triply and more-than triplybranched isotridecanols in the resultant isotridecanol was 45.8%, thatof doubly branched isotridecanols was 36.8%, and the proportion ofsingly branched isotridecanols together with n-tridecanol was determinedat 17.4%. The procedure here was as follows:

[0066] A specimen of the isotridecanol was trimethylsilylated using 1 mlof N-methyl-N-trimethylsilyltrifluoroacetamide per 100 μl of specimenfor 60 minutes at 80° C. For separation by gas chromatography use wasmade of a Hewlett Packard Ultra 1 separating column of 50 m in length,based on 100%-methylated silicone rubber, with an internal diameter of0.32 mm, with a film thickness of 0.33 μm. Injector temperature anddetector temperature were 250° C. and the oven temperature was 160° C.(isothermal). The split was 80 ml/min. The carrier gas was nitrogen. Theinlet pressure was set to 2 bar. 1 μl of the specimen was injected intothe gas chromatograph, and the separated constituents were detected bymeans of FID. For evaluation purposes the gas chromatogram wassubdivided into the following regions: Region 1 Retention index <1180Region 2 Retention index from 1180 to 1217 Region 3 Retention index>1217.

[0067] The reference substances used here were n-undecanol Retentionindex 1100 n-tridecanol [sic] Retention index 1200 and n-tridecanolRetention index 1300.

[0068] The areas of the tridecanol peaks were set to 100 percent byarea.

[0069] The density of the isotridecanol was 0.843 g/cm³, the refractiveindex n_(D) ²⁰ was 1.448, the viscosity was 34.8 mPas, and the boilingrange was from 261 to 267° C.

Example 2

[0070] Preparation and testing of an inventive diester of the inventionmade from phthalic acid and from a mixture of decanols and tridecanolsin a molar ratio of 70:30

[0071] 307.81 g of the isotridecanol from Example 1 and 569.09 g of amixture of 2-propylheptanol and 4-methyl-2-propylhexanol in a ratio byweight of 89:11 (20% alcohol excess, based on phthalic anhydride) werereacted with 316.98 g of phthalic anhydride and 0.41 g of isopropylbutyl titanate as catalyst, in a 2 l autoclave into which N₂ was bubbled(10 l/h) at 230° C. using a stirring rate of 500 rpm. The water ofreaction formed was continuously removed with the N₂ stream from thereaction mixture. The reaction time was 180 min. The alcohol excess wasthen distilled off at a reduced pressure of 50 mbar. 1000 g of the crudephthalate were neutralized with 150 ml of 0.5% strength by weight sodiumhydroxide solution by stirring at 80° C. for 10 minutes in order toremove acidic monomer components, e.g. incompletely esterified phthalicacid. A two-phase mixture formed, with an upper organic phase and alower aqueous phase (washings with hydrolyzed catalyst). The aqueousphase was separated off, and the organic phase was washed again twicewith 200 ml of water. For further purification, the neutralized andwashed phthalate was treated with steam at 180° C. at a reduced pressureof 50 mbar for 2 h, low boilers thereby being removed. The purifiedphthalate was then dried for 30 min at 150° C./50 mbar by passing astream of N₂ (2 l/h) through it, then mixed with activated carbon bystirring for 5 min and filtered off with suction at 80° C. through afilter funnel using the filtration aid “Supra”-Theorit 5.

[0072] The resultant mixture of diesters had a density of 0.957 g/cm³, aviscosity of 138 mPas, a refractive index n_(D) ²⁰ of 1.483, an acidvalue of 0.027 mg KOH/g, a water content of 0.029% by weight, and apurity of 99.83% by GC.

[0073] 150 g of “Vinoflex S 7114” suspension PVC (Solvin), 100 g of thephthalate of the invention, and 3 g of “Lankromark LZB 753” Ba/Znstabilizer were mixed at room temperature using a manual mixer. Themixture was then plasticized on a steam-heated laboratory roll mill(Collin “150”) and processed to give a milled sheet. The temperature ofeach of the two rolls was 170° C., and the rotation rates were 15 rpm(front roll) and 12 rpm (rear roll), and the milling time was 5 minutes.This gave a milled sheet with a thickness of 0.55 mm. The cooled milledsheet was then pressed at 180° C. at a pressure of 220 bar for 400 s ina Collin “400 P” press to give a plasticized PVC film with a thicknessof 0.50 mm.

[0074] The volatility of the plasticizer was then determined by thefollowing method on this plasticized PVC film:

[0075] A specimen holder for four vertically suspended film specimenswas attached to the inner top surface of a commercially availableHeraeus T 5042 E laboratory drying cabinet of interior dimensions 42(width)×35 (height)×32 (depth) cm. The axis of this sample holder wasdriven by an electric motor at 2 rpm. The dimensions of the filmspecimens were 100×150×0.5 mm. They were weighed before the experimentand then suspended from the specimen holder using a perforation on theshort side of each specimen. The upper edges of the films here were 70mm distant from the top inner surface of the cabinet. Arranged on thefloor of the cabinet there was an air-circulator box, covered with a“Sika B 100” sintered metal sheet and producing a laminar air flowwithin the cabinet. The air throughput was set to 800 l/h, correspondingto an air change rate of from 17 to 18 air changes per hour. Thetemperature of 130° C. was monitored by a temperature sensor whose tiphad been positioned in the middle of the cabinet, 100 mm below the topinner surface. An exhaust tube led from the cabinet interior to acondensation apparatus for the plasticizer. The experiment lasted 24hours, after which the four specimens of film were weighed and theaverage percentage weight loss calculated.

[0076] The cold-crack temperature was determined to DIN 53372, and thetorsional rigidity to DIN 53447. The results are given in Table 1.

Example 3

[0077] Preparation and testing of a diester of the invention made fromphthalic acid and from a mixture of decanols and tridecanols in a molarratio of 50:50

[0078] 505.01 g of the isotridecanol from Example 1 and 398.89 g of amixture of 2-propylheptanol and 4-methyl-2-propylhexanol in a weightratio of 89:11 were reacted, as in Example 2, with 311.05 g of phthalicanhydride and 0.41 g of isopropyl butyl titanate as catalyst.

[0079] The resultant mixture of diesters had a density of 0.953 g cm³, aviscosity of 146.0 mPas, a refractive index n_(D) ²⁰ of 1.483, an acidvalue of 0.027 mg KOH/g, a water content of 0.028% by weight, and apurity of 99.77% by GC.

[0080] Using methods similar to those of Example 2, a plasticized PVCcompound was prepared using the phthalate of the invention, and tested.The results are given in Table 1.

Example 4

[0081] Preparation and testing of a diester of the invention made fromphthalic acid and from a mixture of decanols and tridecanols in a molarratio of 30:70

[0082] 740.68 g of the isotridecanol from Example 1 and 250.73 g of amixture of 2-propylheptanol and 4-methyl-2-propylhexanol in a weightratio of 89:11 were reacted, as in Example 2, with 325.86 g of phthalicanhydride and 0.41 g of isopropyl butyl titanate as catalyst.

[0083] The resultant mixture of diesters had a density of 0.950 g cm³, aviscosity of 157.0 mPas, a refractive index n_(D) ²⁰ of 1.483, an acidvalue of 0.035 mg KOH/g, a water content of 0.027% by weight, and apurity of 99.81% by GC.

[0084] Using methods similar to those of Example 2, a plasticized PVCcompound was prepared using the phthalate of the invention, and tested.The results are given in Table 1.

Examples 5-7 Comparative Examples

[0085] Using methods similar to those in Examples 2 to 4, plasticizedPVC films were prepared using the commercially available plasticizers:BASF Palatinol Z (a diisodecyl phthalate), BASF Palatinol 10-P (adi-2-propylheptyl phthalate), and BASF Palatinol CE 5455 (adiisotridecyl phthalate). Using these films, the volatility of theplasticizer was determined by the method described above, the cold-cracktemperature was determined to DIN 53372 and the torsional rigidity wasdetermined to DIN 53447. The results are given in Table 1. TABLE 1Results of performance tests on plasticizers Volatility (% Cold-crackTorsional weight loss temperature rigidity to from the to DIN DIN 53447specimen) 53372 [° C.] [° C.] Example 2, 0.68 −41 −41 Inventive Example3, 0.54 −42 −43 Inventive Example 4, 0.38 −43 −44 Inventive Example 5,0.9 −36 −35 Comparison: BASF Palatinol Z Example 6, 1.2 −35 −38Comparison: BASF Palatinol 10-P Example 7, 0.5 −30 −37 Comparison: BASFPalatinol CE 5455

[0086] Table 1 shows that the volatility of the plasticizers of theinvention is comparable with, or can even be superior to, that of thebest comparative product, namely BASF Palatinol CE 5455, a diisotridecylphthalate. In addition, the plasticizers of the invention have markedlyimproved, i.e. lower, cold-crack temperatures and torsional rigiditieswhen compared with all three of the comparative products (BASFPalatinols of grades Z, 10-P, and CE 5455).

We claim:
 1. A process for preparing mixtures of diesters of phthalicacid with decanols and tridecanols, which comprises reacting phthalicacid or a reactive derivative of phthalic acid with a mixture made fromat least one decanol and at least one tridecanol.
 2. A process asclaimed in claim 1, wherein the decanol used comprises a mixture ofdecanols composed mainly of 2-propylheptanol and4-methyl-2-propylhexanol.
 3. A process as claimed in claim 1 or 2,wherein the tridecanol used comprises a mixture of isomeric tridecanolsas claimed in any of claims 7 to
 10. 4. A process as claimed in any ofclaims 1 to 3, wherein the mixture made from at least one decanol andfrom at least one tridecanol comprises from 65 to 75 mol % of decanoland from 35 to 25 mol % of tridecanol.
 5. A process as claimed in any ofclaims 1 to 4, wherein the mixture made from at least one decanol andfrom at least one tridecanol is used in a molar excess of from 20 to30%, based on phthalic acid or on the reactive derivative of phthalicacid.
 6. A mixture of diesters of phthalic acid, obtainable by theprocess as claimed in any of claims 1 to
 5. 7. A mixture of diesters ofphthalic acid with decanols and tridecanols, comprising from 38 to 45%by weight of diesters with two C₁₀ alcohols, from 40 to 48% by weight ofdiesters with one C₁₀ alcohol and one C₁₃ alcohol, and from 10 to 15% byweight of diesters with two C₁₃ alcohols.
 8. The use of the mixtures ofdiesters of phthalic acid as claimed in claims 6 or 7 as plasticizersfor molding compositions, in particular PVC-based molding compositions.9. A mixture of isomeric tridecanols which comprises from 20 to 60% oftriply or more-than-triply branched tridecanols, from 10 to 50% ofdoubly branched tridecanols, and from 5 to 30% of singly branchedtridecanols and/or of n-tridecanol, where the percentages give the areasdetermined by gas chromatography relative to the total area over all ofthe tridecanols present in the mixture analyzed, and where the mixturesare obtained by hydroformylation and hydrogenation of a mixture ofisomeric dodecenes.
 10. A mixture of isomeric tridecanols as claimed inclaim 9, in the preparation of which as claimed in claim 9 the mixtureof isomeric dodecenes is obtained by reacting a hydrocarbon mixturecomprising butenes on a heterogeneous catalyst which comprises nickeloxide.
 11. A mixture of isomeric tridecanols as claimed in claim 9, inthe preparation of which as claimed in claim 9 or 10 the heterogeneouscatalyst which comprises nickel oxide comprises, as substantial activeconstituents, from 10 to 70% by weight of nickel oxide, from 5 to 30% byweight of titanium dioxide and/or zirconium dioxide, and from 0 to 20%by weight of aluminum oxide, the remainder, to give 100% by weight,being silicon dioxide.
 12. A mixture of isomeric tridecanols as claimedin claim 9, in the preparation of which as claimed in any of claims 9 to11 the hydroformylation takes place in the presence of a cobaltcatalyst.